Heretofore, such as shown in U.S. Pat. No. 3,943,974 dated Mar. 16, 1976, a control valve for a fluid actuator has a slide valve member mounted within a housing with a piston on one end and a knob on the other end. A spring is provided to urge the slide valve and piston to a seated position so that upon an exhausting of fluid from the piston chamber the piston will move rapidly to a seated position thereby to permit the subsequent exhaust of fluid from the actuator for closing of the associated valve. In the event of a failure of the spring, it is possible that the piston would not move to the seated position which would thereby prevent the valve in the main flowline from moving to a closed position. As shown in U.S. Pat. No. 3,877,484 dated Apr. 15, 1975, a differential area on the valve member is provided to effect movement of the piston upon an exhaust fluid from the pressurized piston chamber.